Heat shock activation of telomeric sequences in different tissues of Chironomus thummi.

The heat shock transcription factor (HSF) has been found by immunocytochemistry using the Drosophila HSF antibody at T-BRIII, a telomeric heat shock-induced puff in polytene chromosomes of Chironomus thummi salivary glands. Other heat shock-activated loci were also positively stained by the antibody. Neither the telomeres nor other heat shock loci were labeled under control conditions. These results support the presence of a heat shock gene at T-BRIII despite its peculiar location and molecular organization, different from other well-characterized heat shock genes in Diptera. This locus is similarly induced and transcribed under heat shock in Malpighian tubules, another larval polytenic tissue. Transcription from telomeric-associated sequences has also been found in control polytenic and diploid tissues. The meaning of transcription and heat shock activation of telomeric sequences is discussed in relation to the organization of telomeres and compared to possible equivalents in other known heat shock loci.